a) While sneaking, wall crawling should not happen (not upwards).
b) Wall climbing needs a way to be disabled temporarily.

Good idea, wall climb is now disabled when sneaking.
Also, activating the anti-field orb will disable wall climbing.

The orb blocks walk climbing when "shimering", is your's not doing that?

Also, to the idea of a specific orb. There's a bigger re-write coming of the mod that will let you do that.

It blocks wall climbing when NOT blocking item/XP magnet. I assume it should behave the same for all uses.

The orb works the wrong way around. Also I'd like to suggest a specific orb (craft with a string) to selectively only disable spider power.

Actually, the item/XP magnets were wrong... they checked only if the anti-field existed in inventory, not that it was "on". This has been fixed in 1.24